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[Editor’s note: In calling for a ban on artificial nails in its hand hygiene draft, the Centers for Disease Control and Prevention cited these two articles as well others in the literature.]
Hedderwick SA, McNeil SA, Kauffman CA. Pathogenic organisms associated with artificial fingernails worn by healthcare workers. Infect Control Hosp Epidemiol 2000; 21:505-509.
Artificial fingernails were more likely to harbor pathogens, especially gram-negative bacilli and yeasts, than natural nails, the authors found. "The longer artificial nails were worn, the more likely that a pathogen was isolated," they concluded. "Current recommendations restricting artificial fingernails in certain health care settings appear justified," the researches said. In the study, the quantities of all organisms were greatest in the subungual region of the nails. The researchers also found that quantities of potential pathogens were higher in the subungual area.
Two separate studies were undertaken to determine the differences in the identity and quantity of microbial flora from health care workers wearing artificial nails compared with control workers with natural nails.
In the first study, 12 health care workers who did not normally wear artificial nails wore polished artificial nails on their nondominant hand for 15 days. Identity and quantity of microflora were compared between the artificial nails and the polished natural nails of the other hand. In the second study, the microbial flora of the nails of 30 health care workers who wore permanent acrylic artificial nails were compared with that of control workers who had natural nails.
In both studies, nail surfaces were swabbed and subungual debris was collected to obtain material for culture. Staphylococcus aureus, gram-negative bacilli, enterococci, and yeasts were considered to be potential pathogens. All organisms were identified and quantified. In study one, potential pathogens were isolated from more samples obtained from artificial nails than native nails (92% vs. 62%).
Colonization of artificial nails increased over time; by day 15, 71% of cultures yielded a pathogen compared with 21% on day one. More organisms were found on the surface of artificial nails than natural nails but there were no differences noted in the quantities of organisms isolated from the subungual areas.
In study two, health care workers wearing artificial nails were more likely to have a pathogen isolated than controls. More health care workers with artificial nails had gram-negative bacilli and yeasts than control workers.
Moolenaar RL, Crutcher M, San Joaquin VH, et al. A prolonged outbreak of Pseudomonas aeruginosa in a neonatal intensive care unit: Did staff fingernails play a role in disease transmission? Infect Control Hosp Epidemiol 2000; 21:80-85.
Epidemiological evidence demonstrated an association between acquiring Pseudomonas aeruginosa and exposure to two nurses. Genetic and environmental evidence supported that association and suggested, but did not prove, a possible role for long or artificial fingernails in the colonization of workers hands with P. aeruginosa, researchers reported. "Requiring short natural fingernails in neonatal intensive care units (NICUs) is a reasonable policy that might reduce the incidence of hospital-acquired infections," they concluded.
To describe an outbreak of P. aeruginosa bloodstream infection (BSI), the authors undertook a 15-month cohort study followed by a case-control study.
They also did an environmental survey and did molecular typing of available isolates using pulsed-field gel electrophoresis. Of 439 neonates admitted during the study period, 46 acquired P. aeruginosa; 16 (35%) of those died. Fifteen (75%) of 20 patients for whom isolates were genotyped had genotype A, and three (15%) had genotype B.
Of 104 health care workers from whom hand cultures were obtained, P. aeruginosa was isolated from three nurses. Cultures from nurses A-1 and A-2 grew genotype A, and cultures from nurse B grew genotype B. Nurse A-1 had long natural fingernails, nurse B had long artificial fingernails, and nurse A-2 had short natural fingernails. On multivariate logistic regression analysis, the exposure to nurse A-1 and exposure to nurse B were each independently associated with acquiring a BS1 or colonization with P. aeruginosa. Other variables, including exposure to nurse A-3, were not.
"The two implicated nurses’ hands were each notable for long fingernails," the authors noted. "One had long natural fingernails, and the other had long artificial fingernails. The third colonized nurse, who was not epidemiologically associated with infection, had short natural fingernails," they wrote.
Among health care workers studied in the environmental survey, those having short- or medium-length natural fingernails had a reduced risk of being colonized with P. aeruginosa, compared to those having long natural or artificial fingernails. When the NICU policy to restrict the use of long or artificial nails was implemented and hand washing was emphasized, fewer BSIs were noted initially, and, when they did recur, different genotypes were identified. Genotype A did persist, however, and a change in the fingernail policy did not prevent further cases from occurring.